The only permissible nuclear reactors should be reactors that are capable of sustaining a catastrophic and shattering destruction of the plant facilities, including the reactor core, such as by direct bombardment, without permanently damaging the environment. The main requirement is that the design should enable any pieces of nuclear material to be located and collected after such a catastrophe so that no considerable, lasting radioactivity is irretrievably left in the environment. The environment should be able to be restored to within 5 times its normal, pre-disaster background radiation levels within 1 year of a catastrophic event. Nuclear reactors which do not meet this requirement should be phased out or even actively removed within a time frame not exceeding 30 years.
The same criteria should apply to military reactors, such as those aboard ships and submarines. If anything, these reactors are unquestionably more likely to be catastrophically destroyed than civilian reactors due to their being primary military targets.
Two current reactor designs that appear sufficiently safe are the Modular High Temperature Gas Cooled Reactor and the lead-cooled Integral Fast Breeder Reactor system with on-site reprocessing.
Nuclear reactors that do not meet the above safety standards, should not have any critical infrastructures sited on land which naturally sit below 100 feet above mean sea level to prevent against potential tsunamis-related disasters.